Reading David Frost's answer just now, reminded of the Moose, I just had the thought - would a ballute increase survivability for the MOOSE?
A ballute is an inflatable parachute. You can deploy it at a much earlier stage in re-entry than a conventional parachute. Result is that more of the heat of re-entry gets absorbed by the ballute and less by whatever it is that is attached to it. So less protection is needed and you can decelerate more fragile loads. It's also being considered for Mars landings.
This is an actual photograph of a ballute as it starts to inflate, from 2012 (cross between a balloon and a parachute)
And, turns out that back in 1966, someone did have this idea - or very similar, a balloon. Thanks for Ben Brown for telling me about this in the comments.
More about these early designs here:
Space Rescue (page 258)
More recently the idea of a ballute like design has come back into favour.
First a Russian design, which was tested a couple of times around 2000:
IRDT
It was 100 kg and could return a mass of up to 250 kg from the ISS, had a two stage process first inflate the inflatable aeroshell and then a ring around it for more resistance at lower altitudes and speeds. Finally for fragile cargo like humans would need a third method to slow right down for landing.
In their tests unfortunately they couldn't find the vehicle after re-entry so couldn't assess how well it worked or otherwise, and the project was halted.
But NASA is looking into this again, it's become easier now, due to new materials, and are working on this right now:
NASA Launches Hypersonic Inflatable Heat Shield Prototype (2012)
They are now working on a Low-Density Supersonic Decelerator - the idea is a ballute pulls out a parachute
First LDSD Test flight a success
They are still working on the parachute, you may remember the news story in June of this year: Huge Supersonic Parachute Ripped to Shreds in NASA 'Flying Saucer' Test but the ballute works brilliantly in the tests (originally thought to be the most risky element) inflating in less than half a second.
Here are a couple of photos of it in action from the second test
and in colour:
Thanks to Mark Adler (see comments)
The other idea is, could a more elaborate MOOSE be shaped like a lifting body? Or more like one anyway? Giving it lift means it spends more time in the upper atmosphere, so it has more time to dissipate the heat, and doesn't get quite so hot. It would also help with automatic orientation.
That was the idea of the Crew Return Vehicle
One way or another you've got the same amount of kinetic energy to dissipate, and a lot of it, so I see four ways of making it survivable, at least with near future technology.
So you'd need a rocket motor or some such to do that, as with MOOSE. But with current technology it would have nothing like enough total delta v to act as a lifting rocket to keep you up high as you slow down and descend all the way down through the atmosphere. It could just get you into the upper atmosphere, then the other techniques would be needed to soften your impact.
If we imagine a future with unlimited power in a small space, you could just gradually slow down to a halt with a deceleration at whatever rate you want, say a comfortable 1 g, while remaining above the atmosphere, then once you are hovering over the Earth, just drop gradually, at whatever speed you want to fall through the atmosphere :). But that's totally science fiction at present.
You'd need a propulsion unit small enough to fit in a spacesuit and capable of long duration acceleration of the mass of a human being at over 1 g. If you had that, you could get down to Earth comfortably with no heat dissipation at all.
You could also hover and travel anywhere on the Earth. And accelerate up to orbit, go into orbit, decelerate to a halt hovering over the Earth and come down wherever you want.
But if you are imagining something like this
it wouldn't work because of course it depends on an atmosphere.
This would work however, if you could get it to last long enough for a descent from orbit (not likely with present day technology)
Jet pack
Basically with current technology, for your jet pack to be able to take you into orbit or decelerate and comfortably slow down to a halt, and come back to Earth without relying on the atmosphere to slow you down from your several times faster than a hyper velocity bullet orbital speed - you'd need to strap a Saturn V booster on your back :).
You'd be able to do it with Roger Shawyer's drive, if he is right about its potential, which however, few believe except himself. There are other ideas about how the EM-drive works, if it is a real effect and not experimental data - but not many share his optimism that it could be powerful enough to keep a human hovering in the Earth's gravitational field.
See Robert Walker's answer to Is the significance and/or creditability of the Eagleworks EM Drive hard vacuum tests being unfairly downplayed by the scientific community?
A ballute is an inflatable parachute. You can deploy it at a much earlier stage in re-entry than a conventional parachute. Result is that more of the heat of re-entry gets absorbed by the ballute and less by whatever it is that is attached to it. So less protection is needed and you can decelerate more fragile loads. It's also being considered for Mars landings.
This is an actual photograph of a ballute as it starts to inflate, from 2012 (cross between a balloon and a parachute)
A large trailing ballute has the advantage that it can de-orbit large payloads with minimal protection as the slow down happens higher up in the atmosphere and most of the effects are on the trailing ballute rather than the payload. Page on nasa.gov
And, turns out that back in 1966, someone did have this idea - or very similar, a balloon. Thanks for Ben Brown for telling me about this in the comments.
"American manned rescue spacecraft. Study 1966. The Rockwell SAVER concept provided return of a single crew member in his ejection seat. A nosecap only the size of the seat absorbed most of the re-entry heat.The rest was dissipated through a huge inflatable balloon deployed from the seat. " SAVERSee also Paracone/MOOSE/SAVER/AIRMAT: Escape Pods from Orbit
More about these early designs here:
Space Rescue (page 258)
More recently the idea of a ballute like design has come back into favour.
First a Russian design, which was tested a couple of times around 2000:
It was 100 kg and could return a mass of up to 250 kg from the ISS, had a two stage process first inflate the inflatable aeroshell and then a ring around it for more resistance at lower altitudes and speeds. Finally for fragile cargo like humans would need a third method to slow right down for landing.
In their tests unfortunately they couldn't find the vehicle after re-entry so couldn't assess how well it worked or otherwise, and the project was halted.
But NASA is looking into this again, it's become easier now, due to new materials, and are working on this right now:
NASA Launches Hypersonic Inflatable Heat Shield Prototype (2012)
They are now working on a Low-Density Supersonic Decelerator - the idea is a ballute pulls out a parachute
They are still working on the parachute, you may remember the news story in June of this year: Huge Supersonic Parachute Ripped to Shreds in NASA 'Flying Saucer' Test but the ballute works brilliantly in the tests (originally thought to be the most risky element) inflating in less than half a second.
Here are a couple of photos of it in action from the second test
The other idea is, could a more elaborate MOOSE be shaped like a lifting body? Or more like one anyway? Giving it lift means it spends more time in the upper atmosphere, so it has more time to dissipate the heat, and doesn't get quite so hot. It would also help with automatic orientation.
That was the idea of the Crew Return Vehicle
- Aeroshell or coating that absorbs much of the heat so it doesn't get to you. In future maybe we'll have thin coatings that take up and reflect all the heat. So far we don't have that, so you only have the Aeroshell, with a thick ablative layer to do the trick.
- Large ballute or other component that absorbs all the heat instead of you
- Lifting body or other method to spread the heat over a longer period of time - this could also include descent rockets for lift during re-entry - or any future tech propulsion method - the idea is to keep you in the upper atmosphere for longer as you slow down with slower heat dissipation in the thinner upper atmosphere.
So you'd need a rocket motor or some such to do that, as with MOOSE. But with current technology it would have nothing like enough total delta v to act as a lifting rocket to keep you up high as you slow down and descend all the way down through the atmosphere. It could just get you into the upper atmosphere, then the other techniques would be needed to soften your impact.
If we imagine a future with unlimited power in a small space, you could just gradually slow down to a halt with a deceleration at whatever rate you want, say a comfortable 1 g, while remaining above the atmosphere, then once you are hovering over the Earth, just drop gradually, at whatever speed you want to fall through the atmosphere :). But that's totally science fiction at present.
You'd need a propulsion unit small enough to fit in a spacesuit and capable of long duration acceleration of the mass of a human being at over 1 g. If you had that, you could get down to Earth comfortably with no heat dissipation at all.
You could also hover and travel anywhere on the Earth. And accelerate up to orbit, go into orbit, decelerate to a halt hovering over the Earth and come down wherever you want.
But if you are imagining something like this
it wouldn't work because of course it depends on an atmosphere.
This would work however, if you could get it to last long enough for a descent from orbit (not likely with present day technology)
Jet pack
Basically with current technology, for your jet pack to be able to take you into orbit or decelerate and comfortably slow down to a halt, and come back to Earth without relying on the atmosphere to slow you down from your several times faster than a hyper velocity bullet orbital speed - you'd need to strap a Saturn V booster on your back :).
You'd be able to do it with Roger Shawyer's drive, if he is right about its potential, which however, few believe except himself. There are other ideas about how the EM-drive works, if it is a real effect and not experimental data - but not many share his optimism that it could be powerful enough to keep a human hovering in the Earth's gravitational field.
See Robert Walker's answer to Is the significance and/or creditability of the Eagleworks EM Drive hard vacuum tests being unfairly downplayed by the scientific community?
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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